In general, a broadcast service refers to a service in which a transmitter transmits control messages and data traffic to a plurality of unspecified receivers. The transmitter can be a base station (BS), and the receiver can be a mobile station (MS). The BS provides broadcast services using a modulation and coding scheme (MCS) level at which the MSs located in the cell boundary can receive signals. Therefore, even when the channel state is good as all MSs being subject to broadcast service are located in the vicinity of the BS as shown in FIG. 1, the BS transmits signals by applying the lowest MCS level at which the signals can arrive at up to the cell boundary. The signals transmitted using the lowest MCS level are robust against the channel condition but inefficient in terms of resource utilization.
On the other hand, a multicast service refers to a service in which a BS transmits control messages and data traffic to a plurality of specified MSs. At present, 3rd Generation Partnership Project (3GPP) and 3GPP2 define Multimedia Broadcast Multicast Service (MBMS) and Broadcast Multicast Service (BCMCS) as their multicast services, respectively.
However, MBMS and BCMCS have not defined any scheme in which the BS can determine whether the MS has normally received multicast data traffic. Therefore, there is no defined scheme in which the BS can retransmit the multicast data traffic when the MS that has failed to receive the multicast data traffic.